The invention relates generally to seat adjusters and more particularly to an adjustable hinge mount for seats having reclineable backrests, particularly motor vehicle seats, and including a fixed hinge part assigned to the seat proper and a tiltable hinge part assigned to the back rest, and connected by a pivot axle to the fixed hinge part whereby one of the two mount parts are arrestable in an adjusted position of the back rest by arresting means including a ratchet or serrated segment formed on the rotatable hinge part and cooperating with an arresting pawl which is pivotably mounted on the fixed hinge mount. The arresting pawl is controlled by a driven gear rotatably mounted on the fixed hinge part and supporting a cam slidably joining the arresting pawl. A manually controlled two-arm lever is provided with driving gear segments which is engageable with driven gear to rotate the same and thus the cam into an arresting position and into a releasing position of the arresting means.
In a known hinge mount of the above-described type, the hinge part secured to the reclineable back rest is provided with a disc which in the range below the pivot axle is formed with a gear segment. An arresting lever is pivotably mounted on the fixed hinge part assigned to the seat proper and is also formed with arresting gears engageable with the gear segment on the disc of the pivotable hinge part. The arresting lever is arranged so that due to its own weight the arresting gear normally moves out of engagement from the arresting segment of the disc. In order to maintain the desired adjusted inclined position of the back rest relative to the seat part, a setting lever is pivotably mounted on the fixed hinge part and is provided with a cam which urges the arresting arm to move with its arresting piece into or from the engagement with the arresting segment of the disc on the movable hinge part. For this purpose the arresting lever has in the range opposite its arresting piece a back surface which is slidably engaged by the cam attached to the setting lever when the latter is adjusted in the arresting position. At a distance from the back surface of the arresting lever there is provided a projection against which side surface of the cam abuts when the setting lever is moved into is releasing position. As a consequence the working angle of such known cam arrangement is limited and does not exceed the maximum value of about 30.degree. . Since the angle of inclination of the camming surface of the cam has to be lower than that at which self-locking action occurs, the tensioning displacement of the cam at the above-mentioned relatively low inclination angle is also small and consequently it is insufficient both for its primary purpose, namely for securing the engagement of the arresting piece between the movable and fixed hinge parts, and for elimination of manufacturing tolerances between the mutually engaging loaded parts of the hinge mount.